Can I run two Linux distributions on on one hard disk , formatted into one Linux swap, two /root partitions, and one /home partition?
They should be able to share the swap partition, but will there be any problems in sharing the /home partition?, assuming the passwords and login names are the same.
And what about the boot manager. Do I just not install a boot manager on one of the distributions?

No problems what so ever
In this computer I have (apart from Win xp) four different distros and in my other computer I have 8 distros - not all sharing home though
The more like each other the distros are the less problems. Its enough that the login names are the same.
This is from Daryna with the same home as Celena but another password....
As you are to only have two put grub in (hd0) - the default, both times you install. If you don't like the boot order you can edit the menu.lst of the active /boot/grub
Note - if you intend to install a non Ubuntu and an Ubuntu distro don't use the same home and install the Ubuntu based last

Sure - but I would not recommend sharing /home. It's possible - no doubt, but you may have to tinker a bit to avoid settings being messed up.
Another approach is to have separate smaller home partitions and a large storage partition under the home partitions. Perhaps put the Firefox and Thunderbird profiles on separate partition - I've done that.
Install PCLOS first as its installer is not nice to other Linux, Ubiquity - the installer in Mint and Ubuntu - handles other installed Linux gracefully

I would use one home partition. Install PCLOS first and mint second as husse said.

since they both use different DM (KDE and Gnome) you wont have changing settings that occurs when using the same DM from 2 distros (ubuntu and mint).

since you are doing a fresh install of both distros you can test it for yourself.

the thing to remember and check is the user ID set by both OS's for the first user when using a common /home. the first user ID mint uses is 1000, i dont know what UID PCLOS uses but fedora uses a UID or 500. different UID's will cause you heaps of problems, fixable but also a pain.

Maybe I'm wrong, but I was under the impression that the larger the difference the larger the problem - but that is as Boo implies probably only true if you have the the same DM
Have to admit I have not tried it with so different distros

I've been on vacation for awhile and I'm just now getting back to this computer. I think I've found an acceptable solution to my problem but it's not what I originally wanted. I thought a nice neat arrangement of one primary swap partition, two primary / partitions, and an extended partition containing one or two logical /home partitions would work, but I ran into problems.

I installed PCLinuxOS on my raid 0 array(GigaRaid(IT8212)ata raid controller on a GigaByte mb) and everything went well except that it would not give me two primary / partitions. It installed and ran well using the entire raid 0 array, but that's not what I wanted, so I changed the raid 0 array to two normal 60GB drives(still using the GigaRaid controller)and reinstalled PCLinuxOS. I then tried to install Celena on the other 60GB drive but it could not see the raid controller, neither could Ubuntu or even gparted, although the Windows 2000 disk management tool and PCLinuxOS have no trouble working with it.

What I might do now is shrink my 120GB Windows 2000 partition on IDE 1 and install Daryna on it. Or move Win2K to the other 60GB drive and use the IDE 1 drive for Linux distros.

So, for the benefit of other newbies like myself; How do you install multiple distros on one hard drive? I'd like to hear some opinions but this will probably be my last post. Let's move on to something else.

It's very simple, and if you have the knowledge you seem to have there should be no problems.
Gparted can shrink even NTFS partitions (hopefully also with Win2k as it's not the same NTFS as in XP)
Then it's just to create new partitions - make an extended partition as there can only be four primary the extended included. Put swap and home there and as may Linux distros as you like
I have 8 distros in one computer and five on this computer (+ XP) and it's on one disk in both cases